A loss on rental is not necessarily an NOL. Could you give more details  

Unallowed rental losses are calculated and reported on Form 8582.  It shows current year and prior years. No specific year tracking.

Husband & wife have a partnership (Form 1065) and in 2017 purchases a small commercial rental. They are classified as Active Participants and this is the only passive activity they have. They have had losses each year and probably will do so for the next several years. Do I carryover the NOL from one year to the next or are they required to have income from passive activities in the same year as losses in order to carryforward the excess losses is any?

You say the client has loses for the first 3 years - Is this the first year you're preparing this client's return? The returns for the previous years, if prepared correctly, should have Form 8582 attached showing what loss was allowed or unallowed to be carried forward. 

Yes, I am the new accountant for 2019 return. The 2018 return does not record any carryforward from 2017.

I recommend recreating the prior returns in your tax software.  You'll find your answer to the unallowed loss question.  Possibly you'll need to amend a return or two.      

Amending returns to clarify a carry forward which does not affect the tax return seems excessive. My solution is to override the carry forward box and include an explanation attachment. 

George, since the losses came from the 1065 K-1, they would have appeared on the Sch E page 2 had they been allowed. They were suspended, so they were not used in the original years, and they belong on the Sch K-1 worksheet for this year, page 3, section A, lines 1 etc.